decided to test my 'normal' lens. Not a thorough lab quantitative final word test, but as good a test as I could do at home for the purposes of comparing these lens' against one another. So here was the set up:
Canon 6D
Canon 55EX flaash (ceiling bounce)
Adkins test chart printed on high quality glossy paper for extra sharp edges.
Distance was so that 8.5x11 chart about filled a frame.
Tripod and remote shutter.

Each lens was tested at it widest aperture and at ~2 stops down from that. Three lens' were F1.8 and so the two shots were 1.8 and 5.6 the fourth lens was a F2.8 and so was shot at 2.8 and 8.0. All manually focused on 10x Live View

Notice that the Aus Jena(Zeiss) was a bit darker, This was the lens and not an exposure effect. I read that the older Zeiss lens due ot coatings and such were darker(let in less light). In the stopped down shots you will notice that the Zeiss had much better contrast. I believe this is what the coatings etc were adjusted to produce in these lens.

As can be seen the Canon 'Nifty-Fifty' was at the bottom in both tests. although acceptable in the stopped down. Nikon came in a consistent third, and the Pentax and Aus Jena tied in wide open, but the Zeiss won the stopped down do to the better contrast. For my purposes the Pentax and the Jena/Zeiss are kept with the Canon DLSR's (7DmkII and 6D) both work superbly with them using Fotodiox adapters the Aus Jena is an M42 universal screw, and the Pentax a Nikon F mount. The Pentax when used on the crop sensor makes a superb 85mm prime lens.
*NOTE the close ups are about 66% in PS. Absolutely no adjustments were made other than cut crop and paste and resize to 100dpi.